Recently a new type of semiconductor device that is capable of switching significant amounts of electric energy have become known. This device is a form of bilateral insulated gate field effect transistor. The device has a relatively low resistance drop to current flowing through the device and the device is capable of bilateral current flow. The device is further capable of being switched from a conductive to a non-conductive, or a non-conductive to a conductive state by low power with the application of relatively low voltages. This type of device is shown in, for example, U.S. Pat. No. 4,148,046 issued on Apr. 3, 1979 to Hendrickson et al, U.S. Pat. No. 4,148,047 issued on Apr. 3, 1979 to Hendrickson, and in U.S. Pat. No. 4,152,714 to Hendrickson et al, issued on May 1, 1979.
The mode of switching the bilateral insulating gate field effect transistor centers on effectively short circuiting the gate of the insulated gate field effect transistor to the substrate of the device in order to turn the device completely off. The application of a potential to the gate which is greater than the threshold switching voltage for the device causes the device to switch into a full conductive mode. In a P-channel enhancement type of insulated gate field effect transistor, the most positive electrode is normally referred to as the source and the most negative electrode the drain. In order to turn a bilateral insulated gate field effect transistor to the "on" state it is necessary to make the gate more negative than the source by at least the threshold voltage. This threshold voltage is normally in the neighborhood of 2 volts. In order to turn the device "off", it is necessary to connect the gate of the device to the substrate electrode of the device which for all practical purposes shorts the gate to the source. The substrate is normally maintained at the source potential.
The switching characteristics of the bilateral insulated gate field effect transistor are such that some unusual switching circuitry has been developed. In the applications referenced as co-pending with the present application, certain types of control circuits have been disclosed and claimed. These circuits, by and large, all disclose a power source that is available by utilizing a very limited current flow through internal structure that occurs between the source--drain channel of the field effect transistor device and the substrate electrode of the device. By drawing a minor amount of current through the internal structure, as will be explained in connection with the subsequent disclosures, a power source in the form of a charged capacitor can be provided. If this is done, the capacitor is available for switching a single related load and field effect transistor device means. The circuitry developed in the prior art is not readily adaptable to the controlled switching of a number or plurality of individual loads. In the event that a plurality of loads were to be switched, a separate capacitor or power supply would have to be provided for each of the loads. This obviously increases the cost, complexity and size of a solid state device.